Microtome with rotating cutter and specimen feed mechanism supported therewith



Sept. 27', 1949. w A. LADD 2,482,853

MICROTOME WITH ROTATING CUTTER AND SPECIMEN FEED-MECHANISM SUPPORTEDTHEREWITH Filed Feb. 7, 1946 3 Sheets-Sheet 3 49a 50 3 E 0 5 54a 52 /824, f 3/'-"o v I 6 Z 3m 55 Z INVENTOR. W/LL/AM A. LA 00 BY MMM+6MATTORNEYS Patented Sept. 27, 1949 I M FENT' M B T MEW THR TING UT ER NDsmerMnw-Fmn Eonnnasln'sperq p mn rHER wI-Tn" William m l a, Brooklyn, n.x4.

Amman fl b i JCQmpan acorporatjon ofllel'aware AnplicationlFebnuary' 7,IMGySerial Nt'o. 516,120

.e nmi ble Jimmie-fi w rk h fiel -Pf nat ra i0, li i tac ha rre l n ion9 l 'c rubbe M le w. t evn n "in md m j eqerih eebl k nd w eni i n Dueto the extremely small particle size ofllcarbeen mac ie insfiw nit ha ee.i nn h at seth electron .nfi s q pe f u .g no However previog slyknownmi- ;ci'etgmes, have been iou'ncl inadequate for 1 the mg oi ryhhervspecimens of v slufimient thinp ess; pn satis faetoxpik election,mierqsoope examin tiee anfei iont to adapt the. high speed cuttin pgsinqiple, to, the, .progluctlon pf ,su1ficient1y thin WQW$-QQEPSWW w l a rub n l' av it -nee esgary tqn se materially greater outwe ds th fihq re iron- 56 For .in an9e l 1av fel e e uenrl dd i t emplgo ,a lgnife gpeedof the order ,gfj 200-300 miles lpenhour and to. use. a. knife-carrying,mechanisni having high momentum. Even under sueh .perience dni ob ainin$1 5? More hspteq x ens.

JnQwen tovalttaei su cu tin spee s t' wa found'necessary to mount thecuttin edge onfa wheele e mula fld e hhay n 91 idere 'm m t znen iedel'fi ex emely rap yolu- .Wit wum r ee e enfi. a ldit n i vd f r eCPQPEQEGJ h i l ifl axi m w elwll e jy wd sa-na r fn hen-cut in gle ,lpqese enewe it ew ro e hee e .i th position. 9 the eu tine v ed e wi q 19 .t e .m an resu ted in Wide: fillc tiens eet 'iqknes ethe eeetienee df l l-ties ha e n en unterefl Q- lie-ed th .s e ime time the path of 0.e fidge ate uei rmsn d and t leve midsiulfin of he (mi in ed -fin 59inlfih o e t??? of WFh ultnaf n. bim wimen Th ere en inv ntion bro de,am m qve n {My-pr nat o wil .he' .d c ib d with m erencm t e e c empann drawin s which Ion is a.horizontal sectionz along the line13'-.3

speclirnenl holder of ,a micnometerfeeding mech- ;F 1.g Q6. 1shahonizor1ta1z section of the specimen holdenjalong the linezfi -fieofiEig. 4;and

.Eigfl i'sa secti'ona-Lvievwof the knife-holder,

Referring more particularly to Fig. 1, theknizfe or, cutting; edge; is.indicated by the reference numenazlii I: and; isesupponted by. theflywheel 2, fabricated: fwomlah heavymetaliso as tohave momentum.I-Ihe;;flywhee1= is. supported and adapted. ,fimJgxe .drivemby sha jt 3,and is: positioned within chamber 4', -fformed by E bQWI' ShaDGdelementi and acover plate-6 the cover plate being Securely 3 tion ofshaft 3, and is supported at its lower end by the thrust bearing M.

The bearing H rests upon a rubber cushion l5 and is vertically, thoughnon-rigidly, supported by a cushion bushing or sleeve iii of rubber orother resilient material mounted in the upper end of the base stand 9.

A rigid circular disc ll, advantageously of wood or other light materialof consequently relatively low momentum, for supporting a micrometerfeed mechanism, and of suflicient thickness for rigidity, is rigidlysupported by th upper end of bearing I l by means of the collar I8 andset screws I9. The diameter of the disc I! is slightly less than that ofthe bowl so as to provide a small clearance, say about inch.

The specimen is supported by the specimen holder and micrometer feedmechanism 2 I which in turn is rigidly supported by the disc I! by meansof the flange 22 and screws 23.

As shown more clearly in Figs. 4 and 5, the specimen 20 is embedded, asshown, in wax 24, such as conventionally used for this purpose. Thisspecimen is preferably positioned off-center, as shown, for the reasonsto be subsequently stated.

The wax supporting the specimen is contained in the thimble 25, and isprevented from turning within the thimble by means of the screws 26which project into the wax. The thimble is adapted to fit snugly, thoughremovably, into a recession in the upper end of the micrometer feedmechanism shaft 21, and is securely held therein by means of the screwcap 28 and threads 29.

The shaft 21 extends vertically through sleeve 28a, which in turn issupported by the housing 39, rigidly fastened to the disc H, aspreviously described. The lower end of housing 39 supports bracket 3|,which in turn supports a gear train. This gear train in the particularapparatus 11- lustrated is designed to give a reduction ratio of 1667:1and consists of a 100-tooth gear wheel 32 securely fastened to the lowerend of the shaft 21. Gear 32 enmeshes with a 6-tooth pinion gear 33,attached at its lower end to a 100-tooth gear wheel 34, which in turnenmeshes with the worm 35. Worm 35 is directly connected to pulley 39,which is driven by motor 31 through belt 39, ratio control mechanism 39,belt 40, pulley 4|, and belt 42. 43 and 44 represent belt tighteners. Inthe particular apparatus her illustrated, the motor 31 and the series ofpulleys and belts connecting said motor with the worm 35 are such as tovary the speed of the worm from 100 to 1600 R. P. M.

The shaft 2'! is threaded into the sleeve 28a, the threads being cut 52per inch, so that the shaft 21 is fed upwardly, when rotated in theadvancing direction, at the rate of 488 microns per revolution. Thesleeve 29a is provided with split, tapered threads at 45 and 46 wherebyany play may be taken up by the tightening of the threaded adjustingrings 41 and 48.

Because of the extremely rapid rotation of the flywheel carrying theknife I, it is essential that the knife be securely and rigidly fastenedto the flywheel. This is accomplished by means of the knife holder 49,positioned within the flywheel, and projecting through an opening in thecircumference of the flywheel. The outer edge of the knife holder isflush with the circumference of the flywheel and is prevented frommoving beyond this point by means of shoulders 50. The knife blade issecurely held between two half-cylinders 5i, held together by bolt 52.The halfcylinders holding the knife blade between them 4 are rotatablyand removably mounted within the cylindrical housing of the holder 49and are therein secured in the desired position by means of the setscrews 53.

As special precaution against the knifes becoming loosened, I have inthe apparatus illustrated provided the bolt 52 extending through a holein the knife blade, and further have provided the half-cylinders 5| withflanges at their inner end to avoid all possibility of their bein thrownout through the opening in the holder 49 by the terrific centrifugalforce.

An adjustable counter weight 54 is placed diametrically opposite theknife so as to balance the flywheel. The under portion of the fly wheelis shown enclosed by members 55, removably fastened to the flywheel byany convenient means, as by screws 56. The cylindrical housing of theknife holder 49 and the counter weight 54 are fastened to the flywheelby screws 49a and 54a, respectively, passing through the flange thereofas shown in Fig. 3. A cross-sectional view of the knife holder showingthe set screws 53 is represented by Fig. 7 of the drawings.

Because of the hazards involved in the operation of an apparatus of thissort at the required speeds, it is advisable that the bowl 5 and thecover 6 be fabricated of steel of sufficient strength to affordprotection to the operator in the event of any part breaking or comingloose during operation. It is also desirable that lock nuts be usedthroughout the apparatus.

For the purpose of collecting the minute sections of the specimen cut bythe operation, the apparatus is provided with duct 51, as more clear- 1yshown in Figs. 2 and 3 of the drawings, leading from the chamber 4through a glass or other transparent tube 58 to a suction device 59,such as a blower, With means, such as a screen, provided in the lowerend of the transparent tube for supporting a layer 60 of fine fiberssuch as cotton, through which the current of air carrying the specimensmay be drawn from the chamber 4, the specimens contained in said airstream be ing retained on the cotton. By this means the specimens arereadily collected and during the collection may be observed for thepurpose of determining whether the microtome is functioning properly.

In the specific apparatus illustarated, the cutting edge describes acircle of about 15 /2 inches in diameter so that when the fly wheel isturning at a speed of 5000 R. P. M. the cutting speed is about 230 milesper hour. Under such circumstances it is diflicult to maintain a truecutting edge. In the present apparatus this difficulty is alleviated bypositioning the specimen off-center in the wax, as previously described,and by rigidly fastening the specimen to the revolving shaft 21 so thatas said shaft revolves, feeding the specimen into the path of thecutting edge, the portion of the cutting edge which strikes the specimenis continually shifting, thus extending the useful life of the cuttingedge between resharpenings.

Further, by rotatably mounting the half-cylinders which hold the knifeblade, the cutting angle of the knife may be adjusted to any desiredangle.

Microtome knives currently available have in general been found too softfor the high speed cutting of specimens, such as rubber, hereindescribed. For use in my present apparatus I prefer to use a blade ofhighly tempered steel.

In the operation of the apparatus herein described, it is desirable tobring the flywheel to speed and then gradually feed the specimen intothe path of the knife. In discontinuing the operation, the specimenshould be lowered before reducing the speed of the flywheel, for thereason that in operation there is a tendency for the head or flywheel toride at a higher level at top speed than at rest or at lower speeds. I

A further advantage in the mounting of the specimen off-center is thatby so doing one ootains the effect of direct and oblique cutting at allangles with respect to any grain in the sample.

It will be understood from the foregoing description of the apparatusthat the specimen is held relatively stationary except for its rotationand slow advancement into the path of the knife. The flywheel carryingthe knife is, as previously described, designed to operate at very highspeeds. At these high speeds, very slight inaccuracies in balancing theflywheel will result in the axis of rotation precessing, similar to aspinning top. Any attempt to stop this precessing by rigidly holding theupper end of the shaft 3 by an additional bearing, or by fasteningbearings I! and I4 rigidly to the base stand 9 would set up terrificstresses sufficient to bend or break the shaft. In the apparatus shown,axial precession is permitted by the resilient bushing and, by reason ofmy novel arrangement for rigidly supporting the specimen by the bearingl I, any precession of the flywheel is accompanied by a correspondingmovement of the specimen so that no relative movement of the specimenwith respect to the cutting edge is occasioned by axial precession.

By reason of this arrangement, specimens of satisfactory thinness forelectron microscopy may be cut, the actual thickness being controlled byspeed of the knife, the rate at which the specimen is fed into the pathof the cutting edge, the thickness of that cutting edge, and theelimination of relative motion of cutting edge and specimen caused byprecession of the high speed rotating knife or cutting-edge carrier.

I claim:

1. A microtome comprising a shaft rotatably mounted in a bearing, withat least one end thereof projecting beyond one end of the bearing, acutting edge supported by and rigidly connected with a projecting end ofsaid shaft, means for rotating said shaft within the bearing, amicrometer feed mechanism rigidly supported by said bearing and adaptedto hold a, specimen to be cut and feed said specimen into the path ofthe cutting edge, said feed mechanism comprising a shaft adapted torotate slowly as it moves toward the path of said cutting edge, andmeans for rigidly mounting the specimen on that end of the last saidshaft toward the path of the cutting edge, so that the specimen isslowly rotated as it is moved into the path of the cutting edge.

2. A microtome comprising a shaft rotatably mounted in a bearing, withat least one end thereof projecting beyond one end of the bearing, acutting edge supported by and rigidly connected with a projecting end ofsaid shaft, means for rotating said shaft within the bearing, amicrometer feed-mechanism rigidly supported by said bearing and adaptedto hold a specimen to be cut and feed said specimen into the path of thecutting edge, said feed mechanism comprising a shaft adapted to rotateslowly as it moves toward the path of said cutting edge, and means forrigidly mounting said specimen on that end of the last said shaft towardthe path of the cutting edge in a, position eccentric to the axis of thelast said shaft, so that the specimen is slowly rotated as it moves intothe path of the cutting edge, at the same time moving across the cuttingedge.

3. A microtome comprising a housing, a resilient bushing extendingthrough a wall of said housing and supported thereby, a bearingextending through the bushing and housing and'into the chamber withinsaid housing, a shaft extending through said bearing and supportedthereby and projecting from the inner end of said bearing into thechamber, a flywheel mounted on the inner end of said shaft, a cuttingedge supported by and rigidly connected to said fly wheel, means forrotating said shaft and flywheel within said chamber, a micrometerfeed-mechanism adapted to hold a specimen to be cut and feed it into thepath of the cutting edge, said feed-mechanism being rigidly supported bythe inner end of said bearing and otherwise independently of the housmg.

WILLIAM A. LADD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 198,346 Cairns Dec. 18, 1877305,225 Pumphrey Sept. 16, 1884 474,389 Lafferty May 10, 1892 1,728,843Trunz Sept. 17, 1929 1,797,694 Ott May 24, 1931 1,825,421 Roesch Sept.29, 1931 2,047,400 Walter July 14, 1936 2,107,208 Nankivell Feb. 1, 1938

